The goal of this study is to determine the role of social spaces (locations where social interactions occur) and spatial mobility on risk for chlamydia and gonorrhea among adolescent girls living near the US-Mexico border. Adolescent girls have the highest burden of chlamydia (CT) and gonorrhea (GC) compared to any other age- sex group in the United States. Several studies have begun to examine how neighborhood or community-level structural factors may influence health risks, including sexual risk and sexual violence; however, these studies don't account for mobility of individuals across arbitrary neighborhood boundaries. The exposures and experiences that occur in adolescents' different social spaces shape their own behaviors, including those that put them at higher risk for STI and sexual violence. Mobility may impact not only exposure to different community-level structural factors, but also the number and type of social spaces frequented. Additionally, the rapid increase in the number and type of accessible technologies for communication has greatly impacted the manner in which socialization occurs. Understanding how adolescents incorporate this technology into identification of social spaces and attendance of social activities, may help identify novel targets for sexual health interventions. In this study, we aim to 1) develop categories and measures to describe the types and characteristics of adolescents social spaces, including locations where adolescents may be exposed to sexual violence, and adolescents' patterns of mobility, 2) compare types of social spaces, include the geographic location of these spaces, and patterns of mobility between adolescents testing positive for CT and/or GC and those testing negative, and 3) to use qualitative methods to provide a deeper understanding of the role of communication technology in adolescents' identification of activity spaces and engagement in social activities and related sexual and substance use risk behaviors. To meet these aims, we will conduct a case-control study among adolescent girls (age 15-19 years) in collaboration with a youth center and clinic in a culturally diverse neighborhood with a high proportion of ethnic minorities. Fifty cases (positive test for CT and/or GC) will be referred from the clinic, and 150 controls will be recruited from those seeking family planning/ reproductive health services from the youth center. Participants will be asked to complete an interviewer administered survey including questions about demographics, sexual/reproductive health, sexual and substance use behavior, and exposure to sexual violence, as well as a mapping component to identify social spaces using Google Earth. A sample of cases will be asked to participate in a second, in-depth interview about the use of technology in social activity decision making. This study is consistent with the goals of the NIH ANSWHR PAS (PAS-10-226), offering an interdisciplinary study combining concepts of spatial mobility with a gendered perspective on STI risk among sexually active adolescent girls and will provide a framework to explore innovative structural-level interventions to reduce STI risk among this population.